Log10VSWR

Log10VSWR refers to the base-10 logarithm of the voltage standing wave ratio (VSWR) on a transmission line. It provides a logarithmic scale representation of impedance mismatch, transforming the wide range of VSWR values into a more compact form for analysis or plotting.

VSWR is defined as the ratio of the maximum to the minimum voltage along a line with a mismatch: VSWR = (1 + |Γ|) / (1 − |Γ|), where Γ is the complex or magnitude of the reflection coefficient. Taking the base-10 logarithm gives log10(VSWR). The reflection coefficient itself can be expressed in terms of VSWR as Γ = (VSWR − 1) / (VSWR + 1).

Log10VSWR is not a separate standard specification in RF engineering. It is simply a logarithmic transformation of VSWR, and it is monotonic with VSWR: larger VSWR yields larger log10(VSWR). In some analyses or charts, using log10(VSWR) can help to compress a wide dynamic range of mismatch values and facilitate comparisons, though it does not replace the conventional metrics such as VSWR itself or return loss.

Relating log10(VSWR) to return loss, note that return loss in decibels is RL = −20 log10(|Γ|) and Γ = (VSWR − 1) / (VSWR + 1). Therefore RL can be computed from VSWR, and, if needed, translated into a log10(VSWR) value for alternative visualization or processing.

Typical values: log10(VSWR) = 0 at VSWR = 1 (perfect match); log10(VSWR) ≈ 0.301 for VSWR = 2; ≈0.477 for VSWR = 3; 1.0 for VSWR = 10, and so on.